In the context of the present disclosure, the fuel injection systems concerned are used for injecting fuel into the cylinders of an internal combustion engine.
Without restricting its generality, the description of the state of the art and the invention based on it will refer to a high-pressure injection system, although these problems with the state of the art, and their solution according to the invention, also arise or have an effect in low-pressure injection.
A fuel injection system which works at a high-pressure is generally equipped with a fuel store (“rail”), which is filled with fuel by a high-pressure pump, and is thereby brought up to the pressure level required for high-pressure injection. The high-pressure pump itself is supplied with fuel by a low-pressure fuel pump which takes the fuel out of a fuel tank. From the fuel store, the fuel is introduced into the interior of the cylinder via injection valves.
In general, various measures can be adopted for controlling or regulating the fuel injection system. For example, in the low-pressure zone mechanical regulators can be used with return lines to the tank, and also regulating valves in the high-pressure zone.
Pressure pulsations in the low-pressure circuit are a problem. In the case of high-pressure fuel injection systems, these result primarily from the operation of the high-pressure pump, which is generally designed as a single-piston pump. But with low-pressure injection systems too, pulsations of this type can arise, for example from the injection operation. In order to attenuate these pulsations, in the low-pressure zone use can be made of a fuel pressure damper which, for example, is realized as a spring-loaded membrane. In general, a fuel pressure damper provides a compressible medium which absorbs pressure peaks and evens out pressure troughs, thus functioning overall as a buffer.
In the event of faults in the fuel pressure damper, in particular mechanical faults, pressure drops can occur in the low-pressure circuit. This can have a negative effect on the engine power, the emission values for the engine, and other parameters linked with the operation of the internal combustion engine.